Drum type spray dryer



April 9, 1957 R FED( 2,787,840 A DRUM TYPE SPRAY DRYER Filed June 17,1954 DRUM TYPE SPRAY DRYER Robert lFeix, Frankfurt sam Main, GermanyApplication 4June 17 '1954, Serial No. 437,479

3 Claims. (Cl. 34-57) This invention relates to spray drying, and moreparticularly to methods and apparatus especially adapted for spraydrying powdered fruit, powdered vegetable, pul Verulent chemicalsandtheilike.

lt is an object of this invention to ,provide a yspray ldryer capable.of continuous operation.

.Another object of .the invention is to provide .an improved, 'drum typespray drying apparatus designed 'for continuous operation and effectinga substantially immediate drying of the wet material, at relativelyverylow temperatures.

A still further object of the invention is tto provide a method andapparatus for spray drying foodstuffs sufliciently rapidly as to avoidany detrimental influence on color, aroma or vitamin content of thefoodstuffs.

Other objects, and the manner in which .the same are attained, willbecome apparent Aas this speciication proceeds.

ln the manufacture of dried products, the starting material quite oftenis a wet material which owing to various causes, is rendered plastic 'inthe course of the drying procedure and thus becomes dicu'lt to treatinthe drying apparatus. This plasticity .may b e caused, for example, bythe low melting temperature of some kind of sugar which may be present,because of slow crystallization etc.y A Vtemporary plasticity, however,imperdes the conveyance of the `Inaterial in the dryer. While it listrue that dryers, even ot the spray `drying type, have been proposedheretofore which can 'handle material of the `kind described above,these prior devices sutler from the drawback that they must be stoppedfor discharge purposes, thus involving loss of time and interruption ofthe operation. This stoppage, moreover, has a detrimental influence onthe dried material a good part of which, quite frequently, sticks to thewalls to remain there until it is removed therefrom mechanically, and

more often than not manually, which results in a lengthened exposure tothe drying temperature of 80lO0 C. and 'in a detrimental change in theproperties of the material. Powdered fruit and vegetable products, aswell as many chemicals, are particularly susceptible to being damaged inthis manner.

The invention contemplates a drum type spray dryer designed forcontinuous and uniform operation wherein the 4material is protectedduring treatment and drying is etected substantially immediately and atsuch lowl temperatures as from 45 to 50 C., thus involving a materialsaving in the heat supply. Evaporation takes place, as it didheretofore, in a warm air eddy current which does not require the hightemperatures used in other dryers, including roller dryers. Drying iseffected im mediately, i. e. in about half a second, so any change incolor or aroma, or any detrimental influence on vitamins etc. isavoided. The invention contemplates further that the drying zone isfollowed by a cooling zone wherein the material under treatment isrendered pulverulent to prepare it for an equally continuous dischargefrom the drying apparatus. This cooling zone permits converting StatesPatent ice even thosefproducts whichon drying have becomeprlastic, Yintoa more or less easi1y-pulverizable ,stateso .they .can be conveyedlurtlzier vby means of ldischarge devices, .in .a continuous operation.This is .important also where- Crystallization problems are concernedinasmuch as a rapfid and continuous operation is a prerequisite forretaining the aroma, the added sugar and the vitamins in powdered fruit,for example. Givena slow rotation of Vthedrying drum ata rate of from.about l4 to about l5 revolutions per hour, the complete operationtakesonlya few vminutes or at ,most 1A: hour, most if not all of the ,actualdrying in the air current taking up but Yfractions of 4a second. Thecooling zone may be equipped with a water o rar Cooling system, and evenan interior air cooling system maybe employed it the material has passedAbeyond vthe spraying range.

For carrying out the method according to the invention, a drum typedryeris contemplated which is provided with inlet conduits forthe wetAmaterial vand the warm air which conduits may extend through the axlejournal Ao'f the rotary drum. VIn the interior of the .closed rotarydrum, these combined conduits terminate in a unit comprising a sprayinglnozzlefor the wet material and surlrounding the same, an inlet for thewarm air, which vunit is ecoentrically disposed in the cylindricaldrying chamber inside the drum. This arrangement yields `the largestpossible spraying cone, i. e. the largest possible eitective dryingspace.

,1 mounts for rotation, the drying drum 2 which .carries a ring gear 3driven ybya drive gear 4. When .the idrive vapplies `on .the periphery,as shown in the drawing, asaving in power results; however, a directdrive of the axle is also possible with a closed drum. The drum 2 mayalso be equipped With stationary walls and an open drum cylinderrevolving therebetween. In view of the cooling system required, however,a closed cylinder is preferred. The drum 2, as shown in the drawing, isprovided with circumferential rails 5 by means ot which it is supportedon bearing rolls 6. Where the walls of the drum revolve, as shown in thedrawing, the warm air supply conduit 7 and the wet material supplyconduit 8 surrounded thereby, extend into the interior of the drumthrough the axle journal or shaft A of the drum. Both supply conduitsproceed from the point of entry into the drum interior, along a curvedpath to the inlet openings 9 and 10 which are disposed eccentrically tothe shaft A of the drum, opening 9 being provided in the form of aspraying nozzle or disk designed to spray the Wet material into the warmair eddy current, in the direction of the drum diameter so the materialunder treatment is thrown against the wall of the drum, over the rangeof the spraying cone 14.

Intermediate the wall of the drum and the unit comprising sprayingnozzle 9 and warm air supply 10, an arched stationery partition 11 isarranged which is located near the wall of the drum and is designed tocontrol the air eddies. This partition serves the purpose of separatingthe drying chamber proper with its supply of warm air, from the coolingchamber. Any powder particles which in small quantity, may stick to thispartition, are removed from time to time by a stripping `device so theywill drop on the wall of the drum to be removed With the bulk of thedried material. The cooling zone situated behind the partition may beequipped with any known type of cooling system. Cooling by a few degreesonly is suicient to obtain the effect desired. As shown in the drawing,the stripping device may be provided in the form of stripping members 12which are mounted on the partition 11. Both the partition 11 and thestripping members 12 are stationary and do not take part in therevolution of the drum 2; as shown in the drawing, the partition 11 maybe mounted on the conduits 7 and 8 which are also stationary and do notrotate with the drum. The stripping members 12 are designed to conveythe dried material to a lock or discharge opening 13 (Fig. 1) throughwhich it is removed from the apparatus. The wet air is drawn ott"through an exhaust pipe 15, to be passed through a wet air filter (notshown) if desired.

The4 spray drying method according to the invention proceeds as follows.The wet material is conveyed under pressure, through the conduit 8 tothe nozzle 9, while at the same time Warm airis passed through theconduit 7 to the opening 10. The wet material sprayed from the sprayingnozzle 9 is met by the warm air eddy current and is distributed over thespraying range 14 to be dried substantially immediately, the quantity ofdried material adhering to the wall of the drum depending on thetendency of the material under treatment to be rendered plastic underthe conditions of treatment. Revolution of the drum, however, causes thedried material to pass rapidly into the cooling zone located in back ofthe partition 11 where it is rendered pulverizable. The strippingmembers 12 push the dried material, the bulk of which is a powder,against the front wall toward the discharge opening 13. The wet air isdrawn off through the exhaust pipe 15.

If stationary front walls are provided for the drum 2. the supplyconduits for the wet material and the heated air can be introducedtherethrough directly, eccentrically to the axis of the drum.

I wish it to be understood that I do not desire to be limited to theexact details of construction, design, operation and procedure shown anddescribed as modifications within the scope of the appended claims mayoccur to a person skilled in the art which involve no departure from 4the spirit of the invention nor any sacrifice of the advantages thereof.

I claim:

1. Spray drying apparatus comprising a rotary drum, means for rotatingsaid drum, exit means in the wall of the drum for removal of material, asupply conduit for wet material extending into said drum, a supplyconduit for heated gas concentric with the wet material supply conduit,both conduits terminating in openings eccentric to the axis of the drum,and a stationary partition located in proximity to the drum wall and onthe side nearest the conduit openings, said partition subdividiug theinterior of the drum into a drying chamber and a cooling chamber.

2. Spray drying apparatus comprising a rotary drum, means for rotatingsaid drum, exit means in the wall of the drum for removal of material, asupply conduit for wet material extending into said drum and having aspraying nozzle on its opening, a supply conduit for heated gasconcentric with the wet material supply conduit, the terminal openingsof both conduits being eccentric to the axis of the drum, and astationary partition located in proximity to the` drum wall and on theside nearest the conduit openings, said partition subdividing theinterior of the drum into a drying chamber and a cooling chamber.

3. Spray drying apparatus comprising a rotary drum, means for rotatingsaid drum, exit means in the wall of the drum for removal of material, asupply conduit for wet material extending into said drum and having aspraying nozzle on its opening, a supply conduit for heated gasconcentric with the wet material supply conduit and terminating in aheated gas outlet surrounding said spray ing nozzle, the terminalopenings of both conduits being eccentric to the axis of the drum, and astationary parti tion located in proximity to the drum wall and on theside nearest the conduit openings, said partition subdividing theinterior of the drum into a drying chamber and a cooling chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,080,059 Peebles May 11, 1937 2,452,983 Birdseye Nov. 2, 1948 2,465,963Beardslee Mar. 29, 1949 2,521,442 Birdseye Sept. 5, 1950 2,600,945Vincent June 17, 1952

